An evolutionarily ancient midbrain region, the superior colliculus, can independently carry out visual computations long attributed mainly to the cortex, according to a PLOS Biology study. The work suggests that attention-guiding mechanisms with roots more than 500 million years old help separate objects from backgrounds and highlight salient details.
Researchers report that the superior colliculus—an ancestral visual hub conserved across vertebrates—houses circuitry capable of core “center–surround” computations, a fundamental principle for detecting edges, contrast and salient features in a scene. The findings, published October 16, 2025, in PLOS Biology, indicate that the brain’s ability to parse figure from ground is not confined to the cortex and reflects deep evolutionary heritage. The study was highlighted by the Universidad Miguel Hernández de Elche and ScienceDaily.
Working with mouse brain slices, the team combined patterned optogenetics, electrophysiology and computational modeling. By activating specific retinal pathways and recording responses in the superior colliculus, they showed that activity in the surround can suppress the response to a central stimulus—a hallmark of center–surround processing—supported by cell-type–specific mapping and large-scale simulations.
“For decades it was thought that these computations were exclusive to the visual cortex, but we have shown that the superior colliculus, a much older structure in evolutionary terms, can also perform them autonomously,” said Andreas A. Kardamakis, who leads the Neural Circuits in Vision for Action Laboratory at Spain’s Institute for Neurosciences (IN), a joint center of the Spanish National Research Council (CSIC) and the Miguel Hernández University (UMH) of Elche. “This means that the ability to analyze what we see and decide what deserves our attention is not a recent invention of the human brain, but a mechanism that appeared more than half a billion years ago.”
Co–first author Kuisong Song added that the superior colliculus “not only transmits visual information but also processes and filters it actively, reducing the response to uniform stimuli and enhancing contrasts,” underscoring that selection and prioritization of visual input are embedded in ancient subcortical circuits.
The authors say the results support a hierarchical view of vision in which evolutionarily older structures handle essential, rapid computations that guide orienting behaviors. Understanding how these circuits contribute to attention could, according to the institute’s release, inform research on conditions marked by attentional imbalance or sensory hypersensitivity.
The project involved collaborators at Karolinska Institutet and KTH Royal Institute of Technology in Sweden and at MIT in the United States, with IN CSIC‑UMH researcher Teresa Femenía playing a key experimental role, according to the institute’s announcement. The team is extending the work to live animal models to examine how the superior colliculus shapes attention during goal‑directed behavior.
In related scholarship, Kardamakis and Giovanni Usseglio contributed a 2025 chapter on the evolution of visuomotor neural circuits to Elsevier’s Evolution of Nervous Systems series (edited by J. H. Kaas), reviewing how superior colliculus–like structures across fish, amphibians, reptiles, birds and mammals integrate sensory and motor information to guide gaze. As Kardamakis put it, “Evolution did not replace these ancient systems; it built upon them. We still rely on the same basic hardware to decide where to look and what to ignore.”
